Transplantable lines of dimethylbenz(a)anthracene (DMBA)-induced fibrosarcomas exhibit cross-reactivity in the tumor immunity induced in histocompatible chickens with respect to serum antibody, delayed hypersensitivity (DTH) and transplant rejection. Both humoral and cellular immunity also exhibit cross-reactivity with embryo fibroblasts from the same chicken strain. When SC chickens are injected with DMBA after they have been immunized with one tumor line and exhibit DTH and tumor rejection to that line at the age of 12 weeks, they develop a significantly lower incidence of primary fibrosarcomas than do control chickens during the following 5 months. Preliminary results of studies on organ-specific metastases suggest the presence of organ-specific receptors on the tumor cells which can be blocked by monoclonal antibody.